Along with increased computing power, portability has-been an important hallmark of the electronic age. Some electronic products today are manufactured in handheld packages, where the same component in past years occupied an entire room. Such portability would be meaningless without the availability of similarly portable power supplies, so it is no surprise that batteries have also undergone significant development in storage capability, compactness, and other features.
Many portable electronic devices utilize rechargeable batteries, such as for example sealed lead acid (SLA) batteries. Rechargeable batteries provide a number of advantages over their disposable counterparts, not the least of which significantly increased savings to the user by not having to regularly replace spent batteries with expensive new batteries. Moreover, the use of rechargeable batteries also significantly reduces the disposal of batteries, which often times contain heavy elements that can he safely disposed of without significant cost and/or environmental impact. Rechargeable batteries do have some limitations; however. In particular, it is not uncommon for a rechargeable battery to become either over-or undercharged during a recharging phase due to insufficient control of the recharging process. Over-or undercharged batteries will oftentimes lose their capacity in short order, and thus require replacement which again introduces significant costs in acquiring the new battery and disposing of the old battery.
Rechargeable batteries are particularly prone to over-or undercharging in systems in which there is both a high, power and a low power charger. To date, no appropriate system or method of recharging a battery using high power and low power sources has been developed. For example, a simple approach currently employed is to diode “OR” the high and low power inputs together and regulate the temperature compensated charge voltage to the recommended float voltage. This approach does not use a processor and requires long charge times to properly fully charge the battery pack. In the many circumstances, it is often the case that the input power sources are not available for charging for long periods and therefore the battery would typically be undercharged. If the battery is in a cyclic discharge profile repeated undercharges will cause a rapid loss in battery capacity.
Another current approach is to “OR” the high and low power Inputs together and use a microcontroller to control two different charger states. Typically either a minimum charge current or a timer is used to transition from one charge state to the next. This approach can work well given a fixed input power source, hut can often lead to overcharging if the source can supply more current than expected if the algorithm is timer based. On the other hand, it can lead to undercharging if the input power source provides less current then expected and the algorithm requires a minimum charge current to transition to the next charger state.
Accordingly, there is a need in the art for a system and method of charging a rechargeable battery using one of a high power or low power charger that is adapted to minimize the risk of under-or overcharging the battery. Such a desirable system and method would greatly extend battery performance when in use and significantly extend the life of the rechargeable battery, thereby reducing the overall costs to the user.